In late years, in a wiring process for the manufacture of semiconductor devices, there has been employed CMP (Chemical and Mechanical Polishing) as a technique for forming a groove for forming wiring on an insulation layer, embedding a metal for wiring in the groove by the plating method or the like, removing an excess metal and smoothing the insulation layer including metal wiring.
This is a method including chemically and mechanically polishing a surface of a substance to be polished by a slurry with abrasive particles dispersed therein.
In the CMP technique, there has been used a slurry containing an inorganic abrasive particles such as ceria, alumina, or silica or the like from the past. However, these abrasive particles have high hardness. When a metal layer having low hardness such as copper or the like is polished, there are large problems such as abrasive damages to the surface of a metal to be polished which are called scratches, concave portions formed by excessively polishing the central portion of wiring part of a metal to be polished which are called dishing, and concave portions greater than dishing formed by excessively polishing the central portion of a dense area of wiring pattern including an insulation layer, i.e., an under coat layer which are called erosion.
At present, in order to improve performance of semiconductor devices, the ½ width of wiring on the insulation layer becomes much finer from 130 nm to 90 nm and even to 65 nm, and wiring pattern that is an object to be polished in the wiring process is in a much complicated structure.
If the width of wiring becomes much finer, abrasive damages to the a metal surface to be polished due to scratches cause a breaking of wire, and dishing or erosion causes an increase or deviation in wiring resistance and a short circuit between wirings to be formed on the upper layer, thereby considerably deteriorating the reliability of semiconductor devices and drastically lowering the yield rate.
A scratch is caused by partial excessive polishing due to the hardness of abrasive particles or the existence of an aggregate of abrasive particles. A dishing is caused by excessive polishing due to hard abrasive particles, or addition of a pH regulating agent, an additive or the like, which is accelerated elution of a metal to be polished, used for the purpose of increasing the polishing rate. Erosion is caused by excessive polishing due to hard abrasive particles or a low polishing selectivity with a metal to be polished and an insulation layer or an under coat layer such as a barrier layer for preventing diffusion of a metal.
In order to solve these problems, there has been studied on the suppression of defects such as scratches or the like by reduction of mechanical load on a polished surface by decreasing polishing load. However, a high polishing rate may be difficult to be obtained and the throughput may be worsened.
Then, in order to achieve a high polishing rate even with low polishing load, there has been developed an electrochemical and mechanical polishing (ECMP) with suppressed mechanical polishing action by combining electropolishing and the conventional CMP process. ECMP is capable of obtaining a practical polishing rate even with small load of not more than 1 psi. However, there is a problem such that dishing is easy to proceed as compared to CMP since polishing proceeds by electrolysis of a metal to be polished.
Improvement of a slurry for suppressing the occurrence of defects has also been reviewed in various ways. Abrasive particles contained in the CMP slurry are generally inorganic materials such as alumina or the like, but there has been developed a polishing solution for changing abrasive particles from alumina to much softer silica and further polishing in a pH range of from neutral to alkaline in which elution of a metal to be polished is hardly caused. However, even when silica is used as abrasive particles, scratches are decreased as compared to the case where alumina is used as abrasive particles, but the occurrence of scratches, dishing or erosion cannot be fully suppressed.
Furthermore, in Japanese Patent No. 3172008 (Patent Document 1), there has been disclosed a method employing particles of an organic polymer compound having lower hardness than inorganic abrasive particles as polishing abrasive particles. However, since the organic polymer compound used herein employs resins does not have functional groups such as a methacryl resin, a polystyrene resin and the like, a chemical reaction with a metal to be polished never takes place, and a sufficient polishing rate is not obtained. Thus, such a method cannot be used in the actual process for the manufacture of semiconductor devices.
In order to solve the above problems, for example, in Japanese Patent Laid-open No. 2001-55559 (Patent Document 2), there has been disclosed an aqueous dispersion for CMP containing organic particles having functional groups capable of reacting with a metal to be polished. However, there has been no description on dishing or erosion.
Furthermore, in WO01/17006 (Patent Document 3), there have been disclosed a polishing agent for CMP containing a protective-film forming agent and a water-soluble polymer. The water-soluble polymer used herein is polyacrylic acid, polyacrylamide or the like, but the water-soluble polymer is used for the purpose of suppressing etching. When its combination amount exceeds 0.3 weigh part, a polishing rate is lowered.    Patent Document 1: Japanese Patent No. 3172008    Patent Document 2: Japanese Patent Laid-open No. 2001-55559    Patent Document 3: WO 2001/17006